Thin Film Mainly Comprising Titanium Oxide, Sintered Sputtering Target Suitable for Producing Thin Film Mainly Comprising Titanium Oxide, and Method of Producing Thin Film Mainly Comprising Titanium Oxide

ABSTRACT

Provided is a thin film mainly comprising titanium oxide, wherein the thin film comprises components of Ti, Ag and O and contains 29.6 at % or more and 34.0 at % or less of Ti, 0.003 at % or more and 7.4 at % or less of Ag, and oxygen as the remainder thereof, and O/(2Ti+0.5Ag) as a ratio of oxygen to metals is 0.97 or more. This invention aims to provide a thin film mainly comprising titanium oxide having a high refractive index and a low extinction coefficient, a sintered sputtering target mainly comprising titanium oxide suitable for producing the thin film, and a method of producing a thin film mainly comprising titanium oxide. This invention also aims to provide a thin film that has superior transmittance, minimally deteriorates in reflectance, and is useful as an interference film or a protective film for an optical information recording medium. It is also possible to apply this film to a glass substrate; that is, which can be used as a heat reflective film, an antireflective film, and an interference filter.

TECHNICAL FIELD

The present invention relates to a thin film mainly comprising titaniumoxide having a high refractive index and a low extinction coefficient, asintered sputtering target mainly comprising titanium oxide suitable forproducing the thin film, and a method of producing a thin film mainlycomprising titanium oxide.

BACKGROUND ART

In recent years, technology of high-density optical recording disks suchas high-density optical information recording media capable of rewritingwithout requiring a magnetic head has been developed, and these disksare rapidly being commercialized. In particular, CD-RW appeared for thefirst time in 1977 as a rewritable CD, and is the most popularphase-change optical disk today. This CD-RW has a rewrite cycle ofapproximately 1000 times.

Further, DVD-RW for use as a DVD has been developed and commercialized,and the layer structure of this disk is identical with or similar to thestructure of CD-RW. This DVD-RW has a rewrite cycle of approximately1000 to 10000 times.

These disks record, replay and rewrite information by irradiating anoptical beam to cause an optical change of the recording material suchas its transmittance or reflectance, and are electronic parts that havespread rapidly.

Generally speaking, a phase-change optical disc used as a CD-RW or aDVD-RW has a four-layer structure wherein both sides of a recording thinfilm layer of Ag—In—Sb—Te system or Ge—Sb—Te system or the like aresandwiched between the protective layers of high-melting dielectricssuch as ZnS.SiO₂ or the like, and a silver or silver alloy or aluminumalloy reflective film is additionally provided thereto. Further, inorder to increase the rewrite cycle, an interface layer is providedbetween a memory layer and a protective layer as necessary.

The reflective layer and the protective layer are demanded to have anoptical function capable of increasing the reflectance differencebetween the amorphous portion and the crystal portion of the recordinglayer, and also demanded to have a function of protecting the recordingthin film from moisture and heat deformation as well as a function forcontrolling the thermal conditions upon recording (refer to Non-PatentDocument 1).

In recent years, in order to enable high-capacity and high-densitystorage, an optical recording medium of single-sided double (dual) layerhas been proposed (refer to Patent Document 1). Patent Document 1 has afirst information layer formed on a substrate 1 and a second informationlayer formed on a substrate 2 from the incident direction of the laserbeam, and these information films are laminated so as to face each othervia an interlayer.

In the foregoing case, the first information layer is configured from arecording layer and a first metal reflective layer, and the secondinformation layer is configured from a first protective layer, a secondprotective layer, a recording layer and a second metal reflective layer.In addition, a hard coating layer for protecting the disk from scratchesand contamination or the like, a thermal diffusion layer, and otherlayers may also be arbitrarily formed. In addition, various types ofmaterials have been proposed for the foregoing protective layer,recording layer, reflective layer, and other layers.

The protective layer of high-melting dielectrics must be durable againstrepeated thermal stress caused by the heating and cooling and must notallow such thermal effect to influence the reflective film or otherareas, and it is also required to be thin and have low reflectivity andstrength to prevent alteration. From this perspective, the dielectricprotective layer plays an important role. In addition, needless to say,the recording layer, the reflective layer, the interference film layerand the like are also important from the perspective of enabling theelectronic parts such as CDs and DVDs to fulfill their functionsrespectively.

The respective thin films of a multilayer structure are usually formedwith the sputtering method. This sputtering method is to make a positiveelectrode substrate and a negative electrode target face each other, andgenerates an electric field by applying a high voltage between thesubstrate and the target under an inert gas atmosphere. The sputteringmethod employs a principle where plasma is formed by the collision ofionized electrons and the inert gas at the stage of generating anelectric field, the positive ions in this plasma collide with the target(negative electrode) surface to knock out the constituent atoms of thetarget, and the extruded atoms adhere to the opposing substrate surfaceto form a film.

Under the foregoing circumstances, a target using titanium oxide(TiO_(x)) is being proposed as a sputtering target for forming a heatreflective film and an antireflective film (refer to Patent Document 2).In the foregoing case, Patent Document 2 describes that the specificresistance value is set at 0.35 Ωcm or less in order to stabilize thedischarge during the sputtering, and DC sputtering becomes possible,whereby a film of high refractive index can be obtained.

Nevertheless, since the film transmittance will deteriorate, measures ofsetting the oxygen content to be 35 wt % or more and additionallyintroducing oxygen are being adopted. Moreover, since the depositionrate will deteriorate due to the introduction of oxygen, metal oxide isadded in order to improve the deposition rate. However, there areproblems in its application as precision optics or electronic partsrequiring films having a high refractive index and low absorption. Inparticular, it is considered that there are problems on the shortwavelength side in the vicinity of 400 nm.

[Non-Patent Document 1] “Kogaku” magazine, volume 26, no. 1, pages 9 to15

[Patent Document 1] Publication of Unexamined Japanese Application No.2006-79710 [Patent Document 2] Japanese Patent No. 3836163 DISCLOSURE OFTHE INVENTION Problems Which the Invention Intends to Solve

In light of the foregoing problems, it is an object of this invention toprovide a thin film mainly comprising titanium oxide having a highrefractive index and a low extinction coefficient, a sintered sputteringtarget mainly comprising titanium oxide suitable for producing the thinfilm, and a method of producing a thin film mainly comprising titaniumoxide.

Another object of this invention is to obtain a thin film that hassuperior transmittance, minimally deteriorates in reflectance, and isuseful as an interference film or a protective film for an opticalinformation recording medium. It is also possible to apply this thinfilm to a glass substrate; that is, which can be used as a heatreflective film, an antireflective film, and an interference filter.

Means for Solving the Problems

In order to achieve the foregoing objects, as a result of intense study,the present inventors discovered that it is extremely effective to addsilver or silver oxide to titanium oxide in order to obtain a materialthat maintains transmittance and prevents the deterioration inreflectance without losing its properties as an interference film or aprotective film for an optical information recording medium.

Based on the foregoing discovery, the present invention provides thefollowing.

1) A thin film mainly comprising titanium oxide, wherein the thin filmcomprises components of Ti, Ag and O and contains 29.6 at % or more and34.0 at % or less of Ti, 0.003 at % or more and 7.4 at % or less of Ag,and oxygen as the remainder thereof, and O/(2Ti+0.5Ag) as a ratio ofoxygen to metals is 0.97 or more.2) The thin film mainly comprising titanium oxide according to 1) above,wherein O/Ti as a ratio of oxygen to Ti is 2 or more.3) The thin film mainly comprising titanium oxide according to 1) or 2)above, wherein a refractive index in a wavelength region from 400 to 410nm is 2.60 or more.4) The thin film mainly comprising titanium oxide according to any oneof 1) to 3) above, wherein an extinction coefficient in a wavelengthregion from 400 to 410 nm is 0.1 or less.

5) The thin film mainly comprising titanium oxide according to 4) above,wherein an extinction coefficient in a wavelength region from 400 to 410nm is 0.03 or less.

6) The thin film mainly comprising titanium oxide according to any oneof 1) to 5) above, wherein the thin film is used as an interference filmor a protective film.7) The thin film mainly comprising titanium oxide according to 6) above,wherein the thin film is used as an optical recording medium.8) A sintered sputtering target suitable for producing a thin filmmainly comprising titanium oxide, wherein the target comprisescomponents of Ti, Ag and O, contains the respective components at acomposition ratio of (TiO_(2-m))_(1-n)Ag_(n) (provided 0≦m≦0.5, and0.0001≦n≦0.2), and has a specific resistance of 10 Ωcm or less.9) The sintered sputtering target according to 8) above suitable forproducing a thin film mainly comprising titanium oxide, wherein thetarget comprises components of Ti, Ag and O, contains the respectivecomponents at a composition ratio of (TiO_(2-m))_(1-n)Ag_(n) (provided0≦m≦0.5, and 0.01≦n≦0.2), and has a specific resistance of 10 Ωcm orless.10) The sintered sputtering target according to 8) or 9) above, whereinan average grain size of Ag phase existing in the sintered sputteringtarget is 15 μm or less.11) A method of producing a thin film mainly comprising titanium oxide,wherein a sintered sputtering target, which comprises components of Ti,Ag and O, contains the respective components at a composition ratio of(TiO_(2-m))_(1-n)Ag_(n) (provided 0≦m≦0.5, and 0.0001≦n≦0.2), and has aspecific resistance of 10 Ωcm or less, is used to perform sputteringunder an argon gas atmosphere without oxygen or with 0.1 to 16% ofoxygen, whereby formed on a substrate is a thin film which contains 29.6at % or more and 34.0 at % or less of Ti, 0.003 at % or more and 7.4 at% or less of Ag, and oxygen as the remainder thereof, and in whichO/(2Ti+0.5Ag) as a ratio of oxygen to metals is 0.97 or more.12) The method of producing a thin film mainly comprising titanium oxideaccording to 11) above, wherein, if deposition is performed by way of DCsputtering and an oxygen gas ratio in the sputtering atmosphere isrepresented in b (%), the oxygen gas ratio is adjusted to be in a rangeof 0<b≦83.3n−0.17 when the composition ratio n of Ag in the sputteringtarget is 0.0001≦n≦0.01, and the oxygen gas ratio is adjusted to be in arange of 17n−0.17≦b≦83.3n−0.17 when the composition ratio n of Ag is0.01≦n≦0.2.13) The method of producing a thin film mainly comprising titanium oxideaccording to 11) above, wherein sputtering is performed by adjusting theoxygen gas ratio b to be b=0% when the composition ratio m is in a rangeof 0≦m≦0.05 and the composition ratio n of Ag is 0.0001≦n≦0.01.

EFFECT OF THE INVENTION

As described above, the present invention provides a thin film mainlycomprising titanium oxide having a high refractive index and a lowextinction coefficient, a sintered sputtering target mainly comprisingtitanium oxide suitable for producing the thin film, and a method ofproducing a thin film mainly comprising titanium oxide. The thin filmobtained by the present invention yields a great effect as films andlayers for an optical information recording medium.

In addition, the thin film of the present invention has superiortransmittance, minimally deteriorates in reflectance, and isparticularly useful as an interference film or a protective film for anoptical information recording medium.

The protective layer of high-melting dielectrics must be durable againstrepeated thermal stress caused by the heating and cooling, and must notallow such thermal effect to influence the reflective film or otherareas, and it is also required to be thin and have low reflectivity andstrength to prevent alteration. The thin film mainly comprising titaniumoxide of the present invention has properties that can be applied tosuch a material.

In addition, since the oxygen content during sputtering can be adjustedto be within a low range, the present invention also yields an effect ofbeing able to inhibit the deterioration of the deposition rate.

BEST MODE FOR CARRYING OUT THE INVENTION

The thin film mainly comprising titanium oxide of the present inventioncomprises, as described above, components of Ti, Ag and O, contains 29.6at % or more and 34.0 at % or less of Ti, 0.003 at % or more and 7.4 at% or less of Ag, and oxygen as the remainder thereof, and has acomposition ratio in which O/(2Ti+0.5Ag) as a ratio of oxygen to metalsis 0.97 or more.

The existence of Ag yields an effect of increasing the refractive indexof the thin film. If the amount of Ag is less than 0.003, the effect ofadding Ag is small, and if the amount of Ag exceeds 7.4, the extinctioncoefficient of the thin film in a wavelength region from 400 to 410 nmtends to increase. Thus, it is preferable that the abundance of Ag inthe thin film is 0.03 at % or more and 7.4 at % or less.

Although the reason why the refractive index increases is notnecessarily clear, it is considered to be because silver (Ag) isdispersed as fine particles (nanoparticles and the like) in theamorphous film of titanium oxide.

In certain cases, silver may partially exist as silver oxide (Ag₂O,Ag₂O₂ or the like), but such partial existence as silver oxide does notcause any particular problem, and the improvement in the refractiveindex is similarly acknowledged. The existence of silver oxide can beconfirmed when the peak position of Ag3d is 368.0 eV or less in the XPSanalysis.

The material having a high refractive index obtained as described abovewill become a more favorable material since the possibility of opticalmultilayer film design can be expanded.

The foregoing thin film is an amorphous film, and it is possible toobtain a film in which a refractive index in a wavelength region from400 to 410 nm is 2.60 or more. It is further possible to obtain a thinfilm in which an extinction coefficient in a wavelength region from 400to 410 nm is 0.1 or less, and even 0.03 or less.

The foregoing wavelength region from 400 to 410 nm is the wavelengthregion of a blue laser. As described above, the refractive index is 2.60or more in the foregoing wavelength region, and higher the refractiveindex, the more favorable it is. Moreover, an extinction coefficient of0.1 or less, and even 0.03 or less can be achieved, and lower theextinction coefficient, the more suitable it is for multilayering. Thisthin film mainly comprising titanium oxide is effective as aninterference film or a protective film, and particularly useful as anoptical recording medium.

The foregoing thin film can be produced by using a sintered sputteringtarget having a composition ratio of (TiO_(2-m))_(1-n)Ag_(n) (provided0≦m≦0.5, and 0.0001≦n≦0.2), and a specific resistance of 10 Ωcm or less.

When sputtering is performed in the foregoing case, deposition ispreferably performed in an oxygen-containing atmosphere if the Agcontent is particularly high. Thus, the oxygen in the sputtered filmwill increase. In particular, it is possible to obtain a thin filmmainly comprising titanium oxide having a low extinction coefficient ina wavelength region from 400 to 410 nm by adjusting O/Ti as the ratio ofoxygen to Ti to be 2 or more.

The sintered target of the present invention has a similar componentcomposition as the thin film, but is not the same. Specifically, whereasthe basic components of the target include Ti, Ag and O, the compositionratio of the respective components is (TiO_(2-m))_(1-n)Ag_(n) (provided0≦m≦0.5, and 0.0001≦n≦0.2). In addition, the target has a specificresistance of 10 Ωcm or less.

In the foregoing case, if m exceeds 0.5, the extinction coefficienttends to increase since the oxygen defect becomes too large, andtherefore, m is preferably set to 0.5 or less. In addition, if n is lessthan 0.0001, the effect of adding Ag is small, and if n exceeds 0.2, theextinction coefficient in the case of performing the foregoingdeposition tends to increase. Thus, n is preferably set to 0.0001 ormore and 0.2 or less. Conductivity of the target is required forincreasing the sputtering efficiency, and the target of the presentinvention has such a condition and can be subject to DC sputtering.

Incidentally, as described later, if the composition ratio m is in therange of 0≦m≦0.05 and the composition ratio n of Ag is 0.0001≦n≦0.01,the deposition rate can be considerably adjusted based on the sputteringconditions; that is, based on whether the sputtering atmosphere is to beAr+O₂ gas or only Ar gas. If the composition ratio is 0.05≦m≦0.5 or0.01≦n≦0.2, since the extinction coefficient will increase when thesputtering atmosphere is only Ar gas, it is desirable to use Ar+O₂ gas.In the foregoing case, the target composition will be changed accordingto the purpose of production.

In addition, if the average grain size of the Ag phase existing in thesintered sputtering target is 15 μm or less, DC sputtering can beperformed even more easily. Meanwhile, if the average grain size of theAg phase exceeds 15 μm, abnormal discharge will occur frequently. Thus,the average grain size of the Ag phase is preferably 15 μm or less.

This sintered sputtering target is used to perform sputtering under anargon gas atmosphere without oxygen or with 0.1 to 16% of oxygen,whereby a titanium oxide thin film containing Ag and/or Ag oxide can beformed on a substrate.

Upon producing the thin film, as described above, a sintered sputteringtarget, which comprises Ti, Ag and O, contains the respective componentsat a composition ratio of (TiO_(2-m))_(1-n)Ag_(n) (provided 0≦m≦0.5, and0.0001≦n≦0.2), and has a specific resistance of 10 Ωcm or less, is usedto perform sputtering under an argon gas atmosphere without oxygen orwith 0.1 to 16% of oxygen. Specifically, it is thereby possible to form,on a substrate, a thin film which comprises 29.6 at % or more and 34.0at % or less of Ti, 0.003 at % or more and 7.4 at % or less of Ag, andoxygen as the remainder thereof, and in which O/(2Ti+0.5Ag) as a ratioof oxygen to metals is 0.97 or more.

In the foregoing case, the preferred conditions in producing the thinfilm mainly comprising titanium oxide of the present invention are that,if deposition is performed by way of DC sputtering and an oxygen gasratio in the sputtering atmosphere is represented in b (%), the oxygengas ratio is adjusted to be in a range of 0<b≦83.3n−0.17 when thecomposition ratio n of Ag in the sputtering target is 0.0001≦n≦0.01, andthe oxygen gas ratio is adjusted to be in a range of17n−0.17≦b≦83.3n−0.17 when the composition ratio n of Ag is 0.01

Nevertheless, as described above, if the composition ratio m is in therange of 0≦m≦0.05 and the composition ratio n of Ag is 0.0001≦n≦0.01sputtering can also be performed by adjusting the oxygen gas ratio b tobe b=0%. Specifically, it is possible to perform sputtering capable ofsatisfying the optical properties even without any oxygen leakage, andan effect is yielded in that the deposition rate can be considerablyimproved.

In order to produce the target, as the raw materials, high-purity(normally, 4N or higher) titanium oxide (TiO₂) having an average grainsize of 10 μm or less and high-purity (normally, 3N or higher) silverpowder having an average grain size of 20 μm or less are used. These areblended to achieve the composition ratio of the present invention.

Subsequently, after blending the foregoing raw materials, they are mixedwith a wet ball mill or a dry blender (mixer) so that the silver will beuniformly dispersed in the titanium oxide powder.

After the mixing, the mixed powder is filled in a carbon die and subjectto hot press. The hot press conditions may be changed according to theamount of the sintering material, but hot press is usually performedwithin the range of 800 to 1000° C. and bearing surface pressure of 100to 500 kgf/cm². Nevertheless, these conditions are merely representativeconditions and can be selected arbitrarily, and there is no particularlimitation of such conditions. After the sintering, the sintered compactis machined into a target shape.

Consequently, it is possible to obtain a target in which the basiccomponents thereof are Ti, Ag and O, the respective components arecontained at a composition ratio of (TiO_(2-m))_(1-n)Ag_(n) (provided0≦m≦0.5, and 0.0001≦n≦0.2), and silver (Ag) and/or silver oxide (Ag₂O,Ag₂O₂ or the like) is dispersed as fine particles in the matrix oftitanium oxide.

EXAMPLES

The present invention is now explained in detail with reference to theExamples and Comparative Examples. Incidentally, these Examples aremerely illustrative, and the present invention shall in no way belimited thereby. In other words, the present invention shall only belimited by the scope of claim for a patent, and shall include thevarious modifications other than the Examples of this invention.

Example 1

As the raw materials, titanium oxide (TiO₂) having an average grain sizeof 10 μm and a purity of 4N (99.99%) and silver powder having an averagegrain size of 15 μm and a purity of 3N (99.9%) were used. These rawmaterials were blended to achieve TiO₂:Ag=99:1 (at %) and mixed.

1 kg of the mixed powder was mixed with a wet ball mill so that thesilver is uniformly dispersed in the titanium oxide powder.Subsequently, the mixed powder that was dried until moisture evaporatedwas filled in a carbon die and subject to hot press. The hot pressconditions were 900° C. and bearing surface pressure of 300 kgf/cm². Theobtained sintered compact was machined to prepare a target of φ 152 mmand 5 mmt. Consequently, a target having a density of 96% and a specificresistance of 7 Ωcm was obtained. The grain size of the Ag phase in thetarget was 15 μm. No abnormal discharge occurred during the sputtering.The results are shown in Table 1.

TABLE 1 Abnormal Discharge Specific Sputtering Grain Size of duringTarget Composition Resistance Atmosphere Ag Phase DC Sputtering Example1 TiO₂:Ag = 99:1 at % 7 Ω cm Ar—0.5%O₂ 15 μm None Example 2 TiO₂:Ag =90:10 at % 2 Ω cm Ar—2%O₂ 10 μm None Comparative TiO₂:Ag = 90:10 at % 2Ω cm Ar 10 μm None Example 1 Comparative TiO₂ = 100% >100 Ω cm Ar—2%O₂ —Occurred Example 2 Example 3 TiO₂:Ag = 99.9:0.1 at % 10 Ω cm Ar 10 μmNone Example 4 TiO₂:Ag = 98:2 at % 6 Ω cm Ar—1%O₂ 15 μm None ComparativeTiO₂:Ag = 60:40 at % 0.0003 Ω cm Ar—10%₂ 20 μm None Example 3 Example 5TiO₂:Ag = 90:10 at % 0.5 Ω cm Ar—2%O₂ 5 μm None Example 6 TiO₂:Ag =90:10 at % 0.6 Ω cm Ar—2%O₂ 1 μm None Comparative TiO₂:Ag = 90:10 at %15 Ω cm Ar—2%O₂ 50 μm Occurred Example 4 Comparative TiO₂:Ag = 90:10 at% 2 Ω cm Ar—20%O₂ 10 μm None Example 5 Example 7 T1O₂:Ag = 99:1 at % 7 Ωcm Ar 15 μm None Example 8 TiO₂:Ag = 99.5:0.5 at % 9 Ω cm Ar 10 μm NoneExample 9 TiO₂:Ag = 99.95:0.05 at % 10 Ω cm Ar 1.5 μm None Example 10TiO₂:Ag = 99.99:0.01 at % 10 Ω cm Ar 1.5 μm None Example 11 TiO_(1.9):Ag= 99.95:0.05 at % 0.01 Ω cm Ar—4%O₂ 1.5 μm None Example 12 TiO_(1.5):Ag= 99.99:0.01 at % 0.008 Ω cm Ar—4%O₂ 1.5 μm None Example 13TiO_(1.95):Ag = 99.9:0.1 at % 0.08 Ω cm Ar 5 μm None ComparativeTiO_(1.9):Ag = 99.95:0.05 at % 0.01 Ω cm Ar 1.5 μm None Example 6Comparative TiO_(1.5):Ag = 99.99:0.01 at % 0.008 Ω cm Ar 1.5 μm NoneExample 7

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. As the sputteringconditions, DC sputtering was performed in an Ar gas-0.5% O₂ gasatmosphere with a gas pressure of 0.5 Pa, a gas flow rate of 50 sccm,and a sputtering power of 500 to 1000 w. It was possible to perform DCsputtering without any problem, and it was confirmed that the target hasconductivity.

A sputtered film of 500 Å was formed on the glass substrate. The filmcomposition analyzed with EPMA was Ti: 32.9 at %, Ag: 0.7 at %, O: 66.4at %, O/Ti: 2.02, and O/(2Ti+0.5Ag): 1.00. The refractive index andextinction coefficient of the sputtered film were measured. Therefractive index and extinction coefficient were measured with anellipsometer using a light wavelength of 405 nm. These results are alsoshown in Table 1. Incidentally, the oxygen level in Table 2 is thebalance.

Consequently, the refractive index increased to 2.63, and the extinctioncoefficient considerably decreased to 0.005. Thus, it was possible toform a favorable interference film or protective film for an opticalrecording medium.

TABLE 2 Deposition Film Composition Rate Refractive Extinction Ti (at %)Ag (at %) O (at %) O/Ti O/(2Ti + 0.5Ag) (Å/sec/kW) Index CoefficientExample 1 32.9 0.7 66.4 2.02 1.00 1.4 2.63 0.005 Example 2 31.2 3.5 65.32.09 1.02 1.1 2.73 0.008 Comparative 32.3 3.7 64 1.98 0.96 1.9 2.65 0.23Example 1 Comparative 33.2 0 66.8 2.01 1.01 0.9 2.59 0.004 Example 2Example 3 33.3 0.04 66.66 2.00 1.00 1.7 2.63 0.01 Example 4 32.2 1.466.4 2.06 1.02 1.4 2.67 0.006 Comparative 26.3 17.5 56.2 2.14 0.92 0.82.5 0.15 Example 3 Example 5 31.0 3.6 65.4 2.11 1.03 1.1 2.72 0.008Example 6 31.4 3.5 65.1 2.07 1.01 1.1 2.74 0.007 Comparative — — — — —1.1 — — Example 4 Comparative 30.7 3.1 66.2 2.16 1.05 0.3 2.59 0.005Example 5 Example 7 33.1 0.7 66.2 2.00 0.99 1.8 2.67 0.02 Example 8 33.30.2 66.5 2.00 1.00 1.8 2.66 0.01 Example 9 33.3 0.02 66.68 2.00 1.00 1.62.62 0.007 Example 10 33.3 0.005 66.695 2.00 1.00 1.6 2.61 0.005 Example11 33.4 0.02 66.58 1.99 1.00 0.7 2.61 0.007 Example 12 33.4 0.006 66.5941.99 1.00 0.6 2.60 0.01 Example 13 33.8 0.04 66.16 1.96 0.98 1.6 2.630.09 Comparative 34.3 0.02 65.68 1.91 0.96 1.6 2.58 0.21 Example 6Comparative 39.9 0.006 60.094 1.51 0.75 1.5 2.54 0.34 Example 7

Example 2

As the raw materials, as with Example 1, titanium oxide (TiO₂) having anaverage grain size of 10 μm and a purity of 4N (99.99%) and silverpowder having an average grain size of 10 μm and a purity of 3N (99.9%)were used. These raw materials were blended to achieve TiO₂:Ag=90:10 (at%) and mixed.

1 kg of the mixed powder was mixed with a dry blender so that the silveris uniformly dispersed in the titanium oxide powder. Subsequently, themixed powder was filled in a carbon die and subject to hot press. Thehot press conditions were 920° C. and bearing surface pressure of 350kgf/cm². The obtained sintered compact was machined to prepare a targetof φ 152 mm and 5 mmt. Consequently, a target having a density of 96%and a specific resistance of 2 Ωcm was obtained. The grain size of theAg phase in the target was 10 μm. No abnormal discharge occurred duringthe sputtering.

The results are also shown in Table 1.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. As the sputteringconditions, DC sputtering was performed in an Ar gas-2% O₂ gasatmosphere with a gas pressure of 0.5 Pa, a gas flow rate of 50 sccm,and a sputtering power of 500 to 1000 w. It was possible to perform DCsputtering without any problem, and it was confirmed that the target hasconductivity.

A sputtered film of 500 Å was formed on the glass substrate. The filmcomposition was Ti: 31.2 at %, Ag: 3.5 at %, O: 65.3 at %, O/Ti: 2.09,and O/(2Ti+0.5Ag): 1.02.

The refractive index and extinction coefficient of the sputtered filmwere measured. The refractive index and extinction coefficient weremeasured with an ellipsometer using a light wavelength of 405 nm. Theseresults are also shown in Table 2.

Consequently, the refractive index increased to 2.73, and the extinctioncoefficient considerably decreased to 0.008. Thus, it was possible toform a favorable interference film or protective film for an opticalrecording medium.

Comparative Example 1

In this Comparative Example, the target obtained in Example 2 wassubject to sputtering in an oxygen-free Ar atmosphere. Although it waspossible to perform DC sputtering itself, problems arose in theproperties of the thin film. Specifically, the refractive index of theobtained film decreased to 2.65, and the extinction coefficientincreased to 0.23.

Accordingly, even if the target itself is free from problems, when it issubject to sputtering in an oxygen-free Ar atmosphere, it is notpossible to obtain a favorable thin film. As for Comparative Example 1,the results of the target are shown in Table 1, and the composition andresults of the thin film are shown in Table 2.

As shown in the Tables, the film composition was Ti: 32.3 at %, Ag: 3.7at %, O: 64 at %, O/Ti: 1.98, and O/(2Ti+0.5Ag): 0.96.

Moreover, although several other tests were conducted, it was discoveredthat, in cases where the Ag content exceeds 1.5%, problems arise fromdecrease in the refractive index and increase in the extinctioncoefficient if sputtering is not performed in an argon gas atmospherecontaining 0.1 to 16% of oxygen.

Accordingly, when using the sintered sputtering target of the presentinvention, particularly when the Ag content is 1.5% or more, it ispreferable to perform sputtering in an argon gas atmosphere containing0.1 to 16% of oxygen.

Comparative Example 2

As the raw material, titanium oxide (TiO₂) having an average grain sizeof 10 μm and a purity of 4N (99.99%) was used. Specifically, inComparative Example 2, only TiO₂: 100 (at %) was used without addingsilver powder.

1 kg of this powder was filled in a carbon die and subject to hot press.The hot press conditions were 950° C. and bearing surface pressure of250 kgf/cm². The obtained sintered compact was machined to prepare atarget of  152 mm and 5 mmt. Consequently, the density increased to 97%.Nevertheless, the obtained target had a specific resistance exceeding100 Ωcm. The results are also shown in Table 1.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. As the sputteringconditions, DC sputtering was performed in an Ar gas-2% O₂ gasatmosphere with a gas pressure of 0.5 Pa, a gas flow rate of 50 sccm,and a sputtering power of 500 to 1000 w. Nevertheless, since abnormaldischarge occurred during the DC sputtering and caused an unstablestate, DC sputtering was discontinued and deposition was performed onceagain by way of RF sputtering.

The film composition was Ti: 33.2 at %, Ag: 0 at %, O: 66.8 at %, O/Ti:2.01, and O/(2Ti+0.5Ag): 1.01.

A sputtered film of 500 Å was formed on the glass substrate. Therefractive index and extinction coefficient of the sputtered film weremeasured. The refractive index and extinction coefficient were measuredwith an ellipsometer using a light wavelength of 405 nm. These resultsare also shown in Table 2.

Consequently, the refractive index decreased to 2.59, and the extinctioncoefficient was 0.004. Although there is no particular problem with theextinction coefficient, the refractive index decreased, abnormaldischarge occasionally occurred, and there was a problem in that thestability of DC sputtering would deteriorate considerably.

Example 3

As the raw materials, as with Example 1, titanium oxide (TiO₂) having anaverage grain size of 10 μm and a purity of 4N (99.99%) and silverpowder having an average grain size of 10 μm and a purity of 3N (99.9%)were used. These raw materials were blended to achieve TiO₂:Ag=99.9:0.1(at %) and mixed.

1 kg of the mixed powder was mixed with a dry blender so that the silveris uniformly dispersed in the titanium oxide powder. Subsequently, themixed powder was filled in a carbon die and subject to hot press. Thehot press conditions were 920° C. and bearing surface pressure of 350kgf/cm². The obtained sintered compact was machined to prepare a targetof φ 152 mm and 5 mmt. Consequently, a target having a density of 98%and a specific resistance of 10 Ωcm was obtained. The grain size of theAg phase in the target was 10 μm. No abnormal discharge occurred duringthe sputtering.

The results are also shown in Table 1.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. As the sputteringconditions, DC sputtering was performed in an Ar gas atmosphere with agas pressure of 0.5 Pa, a gas flow rate of 50 sccm, and a sputteringpower of 500 to 1000 w. It was possible to perform DC sputtering withoutany problem, and it was confirmed that the target has conductivity. Thedeposition rate improved considerably to 1.7 Å/sec/kW.

A sputtered film of 500 Å was formed on the glass substrate. The filmcomposition was Ti: 33.3 at %, Ag: 0.04 at %, O: 66.66 at %, O/Ti: 2.00,and O/(2Ti+0.5Ag): 1.00. Incidentally, the Ag composition was analyzedwith SIMS.

The refractive index and extinction coefficient of the sputtered filmwere measured. The refractive index and extinction coefficient weremeasured with an ellipsometer using a light wavelength of 405 nm. Theseresults are also shown in Table 2.

Consequently, the refractive index increased to 2.63, and the extinctioncoefficient was 0.01. Thus, it was possible to form a favorableinterference film or protective film for an optical recording medium.

Example 4

As the raw materials, as with Example 1, titanium oxide (TiO₂) having anaverage grain size of 10 μm and a purity of 4N (99.99%) and silverpowder having an average grain size of 15 μm and a purity of 3N (99.9%)were used.

These raw materials were blended to achieve TiO₂:Ag=98:2 (at %) andmixed.

1 kg of the mixed powder was mixed with a dry blender so that the silveris uniformly dispersed in the titanium oxide powder. Subsequently, themixed powder was filled in a carbon die and subject to hot press. Thehot press conditions were 920° C. and bearing surface pressure of 350kgf/cm². The obtained sintered compact was machined to prepare a targetof φ 152 mm and 5 mmt. Consequently, a target having a density of 96%and a specific resistance of 6 Ωcm was obtained. The grain size of theAg phase in the target was 15 μm. No abnormal discharge occurred duringthe sputtering.

The results are also shown in Table 1.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. As the sputteringconditions, DC sputtering was performed in an Ar gas-1% O₂ gasatmosphere with a gas pressure of 0.5 Pa, a gas flow rate of 50 sccm,and a sputtering power of 500 to 1000 w. It was possible to perform DCsputtering without any problem, and it was confirmed that the target hasconductivity.

A sputtered film of 500 Å was formed on the glass substrate. The filmcomposition was Ti: 32.2 at %, Ag: 1.4 at %, O: 66.4 at %, O/Ti: 2.06,and O/(2Ti+0.5Ag): 1.02.

The refractive index and extinction coefficient of the sputtered filmwere measured. The refractive index and extinction coefficient weremeasured with an ellipsometer using a light wavelength of 405 nm. Theseresults are also shown in Table 2.

Consequently, the refractive index increased to 2.67, and the extinctioncoefficient considerably decreased to 0.006. Thus, it was possible toform a favorable interference film or protective film for an opticalrecording medium.

Comparative Example 3

As the raw materials, as with Example 1, titanium oxide (TiO₂) having anaverage grain size of 10 μm and a purity of 4N (99.99%) and silverpowder having an average grain size of 20 μm and a purity of 3N (99.9%)were used. These raw materials were blended to achieve TiO₂:Ag=60:40 (at%) and mixed.

1 kg of the mixed powder was filled in a carbon die and subject to hotpress. The hot press conditions were 950° C. and bearing surfacepressure of 250 kgf/cm². The obtained sintered compact was machined toprepare a target of φ 152 mm and 5 mmt. Consequently, the densityincreased to 90%. Nevertheless, the obtained target had a specificresistance of 0.0003 Ωcm. The results are also shown in Table 1. Thegrain size of the Ag phase in the target was 20 μm.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. As the sputteringconditions, DC sputtering was performed in an Ar gas-10% O₂ gasatmosphere with a gas pressure of 0.5 Pa, a gas flow rate of 50 sccm,and a sputtering power of 500 to 1000 w.

The film composition was Ti: 26.3 at %, Ag: 17.5 at %, O: 56.2 at %,O/Ti: 2.14, and O/(2Ti+0.5Ag): 0.92.

A sputtered film of 500 Å was formed on the glass substrate. Therefractive index and extinction coefficient of the sputtered film weremeasured. The refractive index and extinction coefficient were measuredwith an ellipsometer using a light wavelength of 405 nm. These resultsare also shown in Table 2.

Consequently, the refractive index was 2.5 and the extinctioncoefficient was 0.15. The extinction coefficient increased and therefractive index decreased. However, abnormal discharge did not occur.This is considered to be a result of the electrical stability of thetarget due to a high Ag content regardless of the grain size of Ag.

Example 5

As the raw materials, as with Example 1, titanium oxide (TiO₂) having anaverage grain size of 10 μm and a purity of 4N (99.99%) and silverpowder having an average grain size of 20 μm and a purity of 3N (99.9%)were used. These raw materials were blended to achieve TiO₂:Ag=90:10 (at%) and mixed.

1 kg of the mixed powder was mixed with a dry blender so that the silveris uniformly dispersed in the titanium oxide powder. Subsequently, themixed powder was filled in a carbon die and subject to hot press. Thehot press conditions were 920° C. and bearing surface pressure of 350kgf/cm². The obtained sintered compact was machined to prepare a targetof φ 152 mm and 5 mmt. Consequently, a target having a density of 95%and a specific resistance of 0.5 Ωcm was obtained. The grain size of theAg phase in the target was 5 μm. No abnormal discharge occurred duringthe sputtering.

The results are also shown in Table 1.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. As the sputteringconditions, DC sputtering was performed in an Ar gas-2% O₂ gasatmosphere with a gas pressure of 0.5 Pa, a gas flow rate of 50 sccm,and a sputtering power of 500 to 1000 w. It was possible to perform DCsputtering without any problem, and it was confirmed that the target hasconductivity.

A sputtered film of 500 Å was formed on the glass substrate. The filmcomposition was Ti: 31.0 at %, Ag: 3.6 at %, O: 65.4 at %, O/Ti: 2.11,0/(2Ti+0.5Ag): 1.03.

The refractive index and extinction coefficient of the sputtered filmwere measured. The refractive index and extinction coefficient weremeasured with an ellipsometer using a light wavelength of 405 nm. Theseresults are also shown in Table 2.

Consequently, the refractive index increased to 2.72, and the extinctioncoefficient considerably decreased to 0.008. Thus, it was possible toform a favorable interference film or protective film for an opticalrecording medium.

Example 6

As the raw materials, as with Example 1, titanium oxide (TiO₂) having anaverage grain size of 10 μm and a purity of 4N (99.99%) and silverpowder having an average grain size of 1 μm and a purity of 3N (99.9%)were used. These raw materials were blended to achieve TiO₂:Ag=90:10 (at%) and mixed.

1 kg of the mixed powder was mixed with a dry blender so that the silveris uniformly dispersed in the titanium oxide powder. Subsequently, themixed powder was filled in a carbon die and subject to hot press. Thehot press conditions were 920° C. and bearing surface pressure of 350kgf/cm². The obtained sintered compact was machined to prepare a targetof φ 152 mm and 5 mmt. Consequently, a target having a density of 91%and a specific resistance of 0.6 Ωcm was obtained. The grain size of theAg phase in the target was 1 μm. No abnormal discharge occurred duringthe sputtering.

The results are also shown in Table 1.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. As the sputteringconditions, DC sputtering was performed in an Ar gas-2% O₂ gasatmosphere with a gas pressure of 0.5 Pa, a gas flow rate of 50 sccm,and a sputtering power of 500 to 1000 w. It was possible to perform DCsputtering without any problem, and it was confirmed that the target hasconductivity.

A sputtered film of 500 Å was formed on the glass substrate. The filmcomposition was Ti: 31.4 at %, Ag: 3.5 at %, O: 65.1 at %, O/Ti: 2.07,and O/(2Ti+0.5Ag): 1.01.

The refractive index and extinction coefficient of the sputtered filmwere measured. The refractive index and extinction coefficient weremeasured with an ellipsometer using a light wavelength of 405 nm. Theseresults are also shown in Table 2.

Consequently, the refractive index increased to 2.74, and the extinctioncoefficient considerably decreased to 0.007. Thus, it was possible toform a favorable interference film or protective film for an opticalrecording medium.

Comparative Example 4

As the raw materials, as with Example 1, titanium oxide (TiO₂) having anaverage grain size of 10 μm and a purity of 4N (99.99%) and silverpowder having an average grain size of 50 μm and a purity of 3N (99.9%)were used. These raw materials were blended to achieve TiO₂:Ag=90:10 (at%) and mixed.

1 kg of the mixed powder was mixed with a dry blender so that the silveris uniformly dispersed in the titanium oxide powder. Subsequently, themixed powder was filled in a carbon die and subject to hot press. Thehot press conditions were 920° C. and bearing surface pressure of 350kgf/cm². The obtained sintered compact was machined to prepare a targetof φ 152 mm and 5 mmt.

Consequently, the obtained target had a density of 97% and a specificresistance of 15 Ωcm. The grain size of the Ag phase in the target was50 μm. Subsequently, although an attempt was made to use the sputteringtarget produced as described above to form a sputtered film on a glasssubstrate, abnormal discharge occurred frequently during the sputteringand deposition was difficult. Thus, the deposition was discontinued.

Comparative Example 5

As the raw materials, as with Example 2, titanium oxide (TiO₂) having anaverage grain size of 10 μm and a purity of 4N (99.99%) and silverpowder having an average grain size of 10 μm and a purity of 3N (99.9%)were used. These raw materials were blended to achieve TiO₂:Ag=90:10 (at%) and mixed.

1 kg of the mixed powder was mixed with a dry blender so that the silveris uniformly dispersed in the titanium oxide powder. Subsequently, themixed powder was filled in a carbon die and subject to hot press. Thehot press conditions were 920° C. and bearing surface pressure of 350kgf/cm². The obtained sintered compact was machined to prepare a targetof φ 152 mm and 5 mmt.

Consequently, the obtained target had a density of 96% and a specificresistance of 2 Ωcm. The grain size of the Ag phase in the target was 10μm.

The results are also shown in Table 1.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. As the sputteringconditions, DC sputtering was performed in an Ar gas-20% O₂ gasatmosphere with a gas pressure of 0.5 Pa, a gas flow rate of 50 sccm,and a sputtering power of 500 to 1000 w. Although it was possible toperform DC sputtering without any problem, the deposition rate wasextremely slow at 0.3 Å/sec/kW, and it was at a level where practicalapplication would be difficult.

A sputtered film of 500 Å was formed on the glass substrate. The filmcomposition was Ti: 30.7 at %, Ag: 3.1 at %, O: 66.2 at %, O/Ti: 2.16,and O/(2Ti+0.5Ag): 1.05.

The refractive index and extinction coefficient of the sputtered filmwere measured. The refractive index and extinction coefficient weremeasured with an ellipsometer using a light wavelength of 405 nm. Theseresults are also shown in Table 2. Consequently, the refractive indexdecreased to 2.59 and the extinction coefficient was 0.005.

Example 7

As the raw materials, as with Example 1, titanium oxide (TiO₂) having anaverage grain size of 10 μm and a purity of 4N (99.99%) and silverpowder having an average grain size of 10 μm and a purity of 3N (99.9%)were used. These raw materials were blended to achieve TiO₂:Ag=99:1 (at%) and mixed.

1 kg of the mixed powder was mixed with a dry blender so that the silveris uniformly dispersed in the titanium oxide powder. Subsequently, themixed powder was filled in a carbon die and subject to hot press. Thehot press conditions were 920° C. and bearing surface pressure of 350kgf/cm². The obtained sintered compact was machined to prepare a targetof φ152 mm and 5 mmt.

Consequently, a target having a density of 98% and a specific resistanceof 7 Ωcm was obtained. The grain size of the Ag phase in the target was15 μm. No abnormal discharge occurred during the sputtering.

The results are also shown in Table 1.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. As the sputteringconditions, DC sputtering was performed in an Ar gas atmosphere with agas pressure of 0.5 Pa, a gas flow rate of 50 sccm, and a sputteringpower of 500 to 1000 w. It was possible to perform DC sputtering withoutany problem, and it was confirmed that the target has conductivity. Thedeposition rate improved considerably at 1.8 Å/sec/kW. Accordingly, itis evident that the deposition rate can be improved considerably byperforming DC sputtering to the target in the Ar gas atmosphere.

A sputtered film of 500 Å was formed on the glass substrate. The filmcomposition was Ti: 33.1 at %, Ag: 0.7 at %, O: 66.2 at %, O/Ti: 2.00,and O/(2Ti+0.5Ag): 0.99.

The refractive index and extinction coefficient of the sputtered filmwere measured. The refractive index and extinction coefficient weremeasured with an ellipsometer using a light wavelength of 405 nm. Theseresults are also shown in Table 2. Consequently, the refractive indexincreased to 2.67, and the extinction coefficient was 0.02. Thus, it waspossible to form a favorable interference film or protective film for anoptical recording medium.

Example 8

As the raw materials, as with Example 1, titanium oxide (TiO₂) having anaverage grain size of 10 μm and a purity of 4N (99.99%) and silverpowder having an average grain size of 10 μm and a purity of 3N (99.9%)were used. These raw materials were blended to achieve TiO₂:Ag=99.5:0.5(at %) and mixed.

1 kg of the mixed powder was mixed with a dry blender so that the silveris uniformly dispersed in the titanium oxide powder. Subsequently, themixed powder was filled in a carbon die and subject to hot press. Thehot press conditions were 920° C. and bearing surface pressure of 350kgf/cm². The obtained sintered compact was machined to prepare a targetof φ 152 mm and 5 mmt.

Consequently, a target having a density of 98% and a specific resistanceof 9 Ωcm was obtained. The grain size of the Ag phase in the target was10 μm. No abnormal discharge occurred during the sputtering.

The results are also shown in Table 1.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. As the sputteringconditions, DC sputtering was performed in an Ar gas atmosphere with agas pressure of 0.5 Pa, a gas flow rate of 50 sccm, and a sputteringpower of 500 to 1000 w. It was possible to perform DC sputtering withoutany problem, and it was confirmed that the target has conductivity. Aswith Example 7, the deposition rate improved considerably at 1.8Å/sec/kW. Accordingly, it is evident that the deposition rate can beimproved considerably by performing DC sputtering to the target in theAr gas atmosphere.

A sputtered film of 500 Å was formed on the glass substrate. The filmcomposition was Ti: 33.3 at %, Ag: 0.2 at %, O: 66.5 at %, O/Ti: 2.00,and O/(2Ti+0.5Ag): 1.00.

The refractive index and extinction coefficient of the sputtered filmwere measured. The refractive index and extinction coefficient weremeasured with an ellipsometer using a light wavelength of 405 nm. Theseresults are also shown in Table 2. Consequently, the refractive indexincreased to 2.66, and the extinction coefficient was 0.01. Thus, it waspossible to form a favorable interference film or protective film for anoptical recording medium.

Example 9

As the raw materials, as with Example 1, titanium oxide (TiO₂) having anaverage grain size of 1 μm and a purity of 4N (99.99%) and silver powderhaving an average grain size of 1.5 μm and a purity of 3N (99.9%) wereused. These raw materials were blended to achieve TiO₂:Ag=99.95:0.05 (at%) and mixed.

1 kg of the mixed powder was mixed with a dry blender so that the silveris uniformly dispersed in the titanium oxide powder. Subsequently, themixed powder was filled in a carbon die and subject to hot press. Thehot press conditions were 920° C. and bearing surface pressure of 350kgf/cm². The obtained sintered compact was machined to prepare a targetof 152 mm and 5 mmt.

Consequently, a target having a density of 98% and a specific resistanceof 10 Ωcm was obtained. The grain size of the Ag phase in the target was1.5 μm. No abnormal discharge occurred during the sputtering.

The results are also shown in Table 1.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. As the sputteringconditions, DC sputtering was performed in an Ar gas atmosphere with agas pressure of 0.5 Pa, a gas flow rate of 50 sccm, and a sputteringpower of 500 to 1000 w. It was possible to perform DC sputtering withoutany problem, and it was confirmed that the target has conductivity. Thedeposition rate improved at 1.6 Å/sec/kW. Accordingly, it is evidentthat the deposition rate can be improved considerably by performing DCsputtering to the target in the Ar gas atmosphere.

A sputtered film of 500 Å was formed on the glass substrate. The filmcomposition was Ti: 33.3 at %, Ag: 0.02 at %, O: 66.68 at %, O/Ti: 2:00,and O/(2Ti+0.5Ag): 1.00.

The refractive index and extinction coefficient of the sputtered filmwere measured. The refractive index and extinction coefficient weremeasured with an ellipsometer using a light wavelength of 405 nm. Theseresults are also shown in Table 2. Consequently, the refractive indexincreased to 2.62 and the extinction coefficient was 0.007. Thus, it waspossible to form a favorable interference film or protective film for anoptical recording medium.

Example 10

As the raw materials, as with Example 1, titanium oxide (TiO₂) having anaverage grain size of 1 μm and a purity of 4N (99.99%) and silver powderhaving an average grain size of 1.5 μm and a purity of 3N (99.9%) wereused. These raw materials were blended to achieve TiO₂:Ag=99.99:0.01 (at%) and mixed.

1 kg of the mixed powder was mixed with a dry blender so that the silveris uniformly dispersed in the titanium oxide powder. Subsequently, themixed powder was filled in a carbon die and subject to hot press. Thehot press conditions were 920° C. and bearing surface pressure of 350kgf/cm². The obtained sintered compact was machined to prepare a targetof φ 152 mm and 5 mmt.

Consequently, a target having a density of 98% and a specific resistanceof 10 Ωcm was obtained. The grain size of the Ag phase in the target was1.5 μm. No abnormal discharge occurred during the sputtering.

The results are also shown in Table 1.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. As the sputteringconditions, DC sputtering was performed in an Ar gas atmosphere with agas pressure of 0.5 Pa, a gas flow rate of 50 sccm, and a sputteringpower of 500 to 1000 w. It was possible to perform DC sputtering withoutany problem, and it was confirmed that the target has conductivity. Thedeposition rate improved at 1.6 Å/sec/kW. Accordingly, it is evidentthat the deposition rate can be improved considerably by performing DCsputtering to the target in the Ar gas atmosphere.

A sputtered film of 500 Å was formed on the glass substrate. The filmcomposition was Ti: 33.3 at %, Ag: 0.005 at %, O: 66.695 at %, O/Ti:2.00, and O/(2Ti+0.5Ag): 1.00.

The refractive index and extinction coefficient of the sputtered filmwere measured. The refractive index and extinction coefficient weremeasured with an ellipsometer using a light wavelength of 405 nm. Theseresults are also shown in Table 2. Consequently, the refractive indexincreased to 2.61 and the extinction coefficient was 0.005. Thus, it waspossible to form a favorable interference film or protective film for anoptical recording medium.

Example 11

As the raw materials, as with Example 1, titanium oxide (TiO₂) having anaverage grain size of 1 μm and a purity of 4N (99.99%), titanium powderhaving an average grain size of 15 μm and a purity of 3N, and silverpowder having an average grain size of 1.5 μm and a purity of 3N (99.9%)were used. These raw materials were blended to achieveTiO_(1.9):Ag=99.95:0.05 (at %) and mixed.

1 kg of the mixed powder was mixed with a dry blender so that the silveris uniformly dispersed in the titanium oxide powder. Subsequently, themixed powder was filled in a carbon die and subject to hot press. Thehot press conditions were 920° C. and bearing surface pressure of 350kgf/cm². The obtained sintered compact was machined to prepare a targetof φ 152 mm and 5 mmt.

Consequently, a target having a density of 98% and a specific resistanceof 0.01 Ωcm was obtained. The grain size of the Ag phase in the targetwas 1.5 μm. No abnormal discharge occurred during the sputtering.

The results are also shown in Table 1.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. As the sputteringconditions, DC sputtering was performed in an Ar-4% O₂ gas atmospherewith a gas pressure of 0.5 Pa, a gas flow rate of 50 sccm, and asputtering power of 500 to 1000 w. It was possible to perform DCsputtering without any problem, and it was confirmed that the target hasconductivity. The deposition rate was 0.7 Å/sec/kW.

A sputtered film of 500 Å was formed on the glass substrate. The filmcomposition was Ti: 33.4 at %, Ag: 0.02 at %, O: 66.58 at %, O/Ti: 1.99,and O/(2Ti+0.5Ag): 1.00.

The refractive index and extinction coefficient of the sputtered filmwere measured. The refractive index and extinction coefficient weremeasured with an ellipsometer using a light wavelength of 405 nm. Theseresults are also shown in Table 2. Consequently, the refractive indexincreased to 2.61 and the extinction coefficient was 0.007. Thus, it waspossible to form a favorable interference film or protective film for anoptical recording medium.

Example 12

As the raw materials, as with Example 1, titanium oxide (TiO₂) having anaverage grain size of 1 μm and a purity of 4N (99.99%), titanium powderhaving an average grain size of 15 μm and a purity of 3N, and silverpowder having an average grain size of 1.5 μm and a purity of 3N (99.9%)were used. These raw materials were blended to achieveTiO_(1.5):Ag=99.99:0.01 (at %) and mixed.

1 kg of the mixed powder was mixed with a dry blender so that the silveris uniformly dispersed in the titanium oxide powder. Subsequently, themixed powder was filled in a carbon die and subject to hot press. Thehot press conditions were 920° C. and bearing surface pressure of 350kgf/cm². The obtained sintered compact was machined to prepare a targetof 152 mm and 5 mmt.

Consequently, a target having a density of 98% and a specific resistanceof 0.008 Ωcm was obtained. The grain size of the Ag phase in the targetwas 1.5 μm. No abnormal discharge occurred during the sputtering.

The results are also shown in Table 1.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. As the sputteringconditions, DC sputtering was performed in an Ar+4% O₂ gas atmospherewith a gas pressure of 0.5 Pa, a gas flow rate of 50 sccm, and asputtering power of 500 to 1000 w. It was possible to perform DCsputtering without any problem, and it was confirmed that the target hasconductivity. The deposition rate was 0.6 Å/sec/kW.

A sputtered film of 500 Å was formed on the glass substrate. The filmcomposition was Ti: 33.4 at %, Ag: 0.006 at %, O: 66.594 at %, O/Ti:1.99, and O/(2Ti+0.5Ag): 1.00.

The refractive index and extinction coefficient of the sputtered filmwere measured. The refractive index and extinction coefficient weremeasured with an ellipsometer using a light wavelength of 405 nm. Theseresults are also shown in Table 2. Consequently, the refractive indexincreased to 2.60 and the extinction coefficient was 0.01. Thus, it waspossible to form a favorable interference film or protective film for anoptical recording medium.

Example 13

As the raw materials, as with Example 1, titanium oxide (TiO₂) having anaverage grain size of 1 μm and a purity of 4N (99.99%), titanium powderhaving an average grain size of 15 μm and a purity of 3N, and silverpowder having an average grain size of 5 μm and a purity of 3N (99.9%)were used. These raw materials were blended to achieveTiO_(1.95):Ag=99.9:0.1 (at %) and mixed.

1 kg of the mixed powder was mixed with a dry blender so that the silveris uniformly dispersed in the titanium oxide powder. Subsequently, themixed powder was filled in a carbon die and subject to hot press. Thehot press conditions were 920° C. and bearing surface pressure of 350kgf/cm². The obtained sintered compact was machined to prepare a targetof φ 152 mm and 5 mmt.

Consequently, a target having a density of 98% and a specific resistanceof 0.08 Ωcm was obtained. The grain size of the Ag phase in the targetwas 5 μm. No abnormal discharge occurred during the sputtering.

The results are also shown in Table 1.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. As the sputteringconditions, DC sputtering was performed in an Ar gas atmosphere with agas pressure of 0.5 Pa, a gas flow rate of 50 sccm, and a sputteringpower of 500 to 1000 w. It was possible to perform DC sputtering withoutany problem, and it was confirmed that the target has conductivity. Thedeposition rate improved to 1.6 Å/sec/kW. Accordingly, it is evidentthat the deposition rate can be improved considerably by performing DCsputtering to the target in the Ar gas atmosphere.

A sputtered film of 500 Å was formed on the glass substrate. The filmcomposition was Ti: 33.8 at %, Ag: 0.04 at %, O: 66.16 at %, O/Ti: 1.96,and O/(2Ti+0.5Ag): 0.98.

The refractive index and extinction coefficient of the sputtered filmwere measured. The refractive index and extinction coefficient weremeasured with an ellipsometer using a light wavelength of 405 nm. Theseresults are also shown in Table 2. Consequently, the refractive indexincreased to 2.63 and the extinction coefficient was 0.09. Thus, it waspossible to form a favorable interference film or protective film for anoptical recording medium.

Comparative Example 6

In this Comparative Example, the target obtained in Example 11 wassubject to sputtering in an oxygen-free Ar atmosphere. Although it waspossible to perform DC sputtering itself, problems arose in theproperties of the thin film. Specifically, the refractive index of theobtained film decreased to 2.58, and the extinction coefficientincreased to 0.21.

Accordingly, even if the target itself is free from problems, when it issubject to sputtering in an oxygen-free Ar atmosphere, it is notpossible to obtain a favorable thin film. As for Comparative Example 6,the results of the target are shown in Table 1, and the composition andresults of the thin film are shown in Table 2.

As shown in the Tables, the film composition was Ti: 34.3 at %, Ag: 0.02at %, O: 65.68 at %, O/Ti: 1.91, and O/(2Ti+0.5Ag): 0.96.

Moreover, although several other tests were conducted, it was discoveredthat, in cases where the Ti content exceeds 34.0%, problems arise fromdecrease in the refractive index and increase in the extinctioncoefficient if sputtering is not performed in an argon gas atmospherecontaining 0.1 to 16% of oxygen.

Accordingly, when using the sintered sputtering target of the presentinvention, particularly when the Ti content is 34.0% or more, it ispreferable to perform sputtering in an argon gas atmosphere containing0.1 to 16% of oxygen.

Comparative Example 7

In this Comparative Example, the target obtained in Example 12 wassubject to sputtering in an oxygen-free Ar atmosphere. Although it waspossible to perform DC sputtering itself, problems arose in theproperties of the thin film. Specifically, the refractive index of theobtained film decreased to 2.54, and the extinction coefficientincreased to 0.34.

Accordingly, even if the target itself is free from problems, when it issubject to sputtering in an oxygen-free Ar atmosphere, it is notpossible to obtain a favorable thin film. As for Comparative Example 7,the results of the target are shown in Table 1, and the composition andresults of the thin film are shown in Table 2.

As shown in the Tables, the film composition was Ti: 39.9 at %, Ag:0.006 at %, O: 60.094 at %, O/Ti: 1.51, and O/(2Ti+0.5Ag): 0.75.

Moreover, although several other tests were conducted, it was discoveredthat, in cases where the Ti content exceeds 34.0%, problems arise fromdecrease in the refractive index and increase in the extinctioncoefficient if sputtering is not performed in an argon gas atmospherecontaining 0.1 to 16% of oxygen.

Accordingly, when using the sintered sputtering target of the presentinvention, particularly when the Ti content is 34.0% or more, it ispreferable to perform sputtering in an argon gas atmosphere containing0.1 to 16% of oxygen.

Summary of Examples and Comparative Examples

The foregoing Examples and Comparative Examples illustratedrepresentative examples. Although not shown in the foregoing Examples,in cases where the composition of the thin film was 29.6 at % or moreand 34.0 at % or less of Ti, 0.003 at % or more and 7.4 at % or less ofAg, and oxygen as the remainder thereof, and O/(2Ti+0.5Ag) as a ratio ofoxygen to metals is 0.97 or more, and further where O/Ti as a ratio ofoxygen to Ti is 2 or more; all cases resulted in a high refractive indexand a low extinction coefficient as with foregoing Example 1 to Example7.

Moreover, when the sputtering target contained the respective componentsat a composition ratio of (TiO_(2-m))_(1-n)Ag_(n) (provided 0≦m≦0.5, and0.0001≦n≦0.2), and contained Ag particles having an average grain sizeof 15 μm or less; the specific resistance was 10 Ωcm or less, andfavorable results were achieved in which no abnormal discharge wasobserved.

INDUSTRIAL APPLICABILITY

The present invention provides a thin film mainly comprising titaniumoxide having a high refractive index and a low extinction coefficient, asintered sputtering target mainly comprising titanium oxide suitable forproducing the thin film, and a method of producing a thin film mainlycomprising titanium oxide. The thin film obtained by the presentinvention can be used as films and layers for an optical informationrecording medium of electronic parts such as CDs and DVDs.

In addition, the thin film of the present invention is particularlyuseful as an interference film or a protective film for an opticalinformation recording medium having superior transmittance and withminimal deterioration in reflectance. Since a protective layer ofhigh-melting dielectrics must be durable against repeated thermal stresscaused by the heating and cooling, and must not allow such thermaleffect to influence the reflective film or other areas, and since it isalso required to be thin and have low reflectivity and strength toprevent alteration; the present invention is useful as such dielectricprotective layer.

In addition, a material having the foregoing properties can also beapplied to architectural glass, automotive glass, CRTs and flat-paneldisplays; that is, such material can also be used as a heat reflectivefilm, an antireflective film, and an interference filter.

1-7. (canceled)
 8. A sintered sputtering target suitable for producing athin film mainly comprising titanium oxide, wherein the target comprisescomponents of Ti, Ag and O, contains the respective components at acomposition ratio of (TiO_(2-m))_(1-n)Ag_(n) (provided 0≦m≦0.5, and0.0001≦n≦0.2), and has a specific resistance of 10 Ωcm or less.
 9. Thesintered sputtering target according to claim 8 suitable for producing athin film mainly comprising titanium oxide, wherein the target comprisescomponents of Ti, Ag and O, contains the respective components at acomposition ratio of (TiO_(2-m))_(1-n) (provided 0≦m≦0.5, and0.01≦n≦0.2), and has a specific resistance of 10 Ωcm or less.
 10. Thesintered sputtering target according to claim 9, wherein an averagegrain size of Ag phase existing in the sintered sputtering target is 15μm or less.
 11. A method of producing a thin film mainly comprisingtitanium oxide, wherein a sintered sputtering target, which comprisescomponents of Ti, Ag and O, contains the respective components at acomposition ratio of (TiO_(2-m))_(1-n)Ag_(n) (provided 0≦m≦0.5, and0.0001≦n≦0.2), and has a specific resistance of 10 Ωcm or less, is usedto perform sputtering under an argon gas atmosphere without oxygen orwith 0.1 to 16% of oxygen, whereby formed on a substrate is a thin filmwhich contains 29.6 at % or more and 34.0 at % or less of Ti, 0.003 at %or more and 7.4 at % or less of Ag, and oxygen as the remainder thereof,and in which O/(2Ti+0.5Ag) as a ratio of oxygen to metals is 0.97 ormore.
 12. A method of producing a thin film mainly comprising titaniumoxide according to claim 11, wherein deposition is performed by way ofDC sputtering and on oxygen gas ratio in the sputtering atmosphere isrepresented in b (%), the oxygen gas ratio is adjusted to be in a rangeof 0<b≦83.3n−0.17 when the composition ratio n of Ag in the sputteringtarget is 0.0001≦n≦0.01, and the oxygen gas ratio is adjusted to be in arange of 17n−0.17≦b≦83n−0.17 when the composition ratio n of Ag is0.01≦n≦0.2.
 13. A method of producing a thin film mainly comprisingtitanium oxide according to claim 11, wherein sputtering is performed byadjusting the oxygen gas ratio b to be b=0% when the composition ratio mis in a range of 0≦m≦0.05 and the composition ratio n of Ag is0.0001≦n≦0.01.
 14. A thin film mainly comprising titanium oxide obtainedby the method of producing a thin film according to claim
 11. 15. Thethin film mainly comprising titanium oxide according to claim 14,wherein a refractive index in a wavelength region from 400 to 410 nm is2.6 or more, and an extinction coefficient in a wavelength region from400 to 410 nm is 0.1 or less.
 16. The thin film mainly comprisingtitanium oxide according to claim 15, wherein O/Ti as a ratio of oxygento Ti is 2 or more.
 17. The thin film mainly comprising titanium oxideaccording to claim 16, wherein an extinction coefficient in a wavelengthregion from 400 to 410 nm is 0.03 or less.
 18. The thin film mainlycomprising titanium oxide according to claim 17, wherein the thin filmis an interference film or a protective film.
 19. The thin film mainlycomprising titanium oxide according to claim 18, wherein the thin filmforms part of an optical recording medium.
 20. The thin film mainlycomprising titanium oxide according to claim 14, wherein O/Ti as a ratioof oxygen to Ti is 2 or more.
 21. The thin film mainly comprisingtitanium oxide according to claim 14, wherein an extinction coefficientin a wavelength region from 400 to 410 nm is 0.03 or less.
 22. The thinfilm mainly comprising titanium oxide according to claim 14, wherein thethin film is an interference film or a protective film.
 23. The thinfilm mainly comprising titanium oxide according to claim 22, wherein thethin film forms part of an optical recording medium.
 24. The sinteredsputtering target according to claim 8, wherein an average grain size ofAg phase existing in the sintered sputtering target is 15 μm or less.